Communication system in digital television

ABSTRACT

Disclosed is a digital communication system. A transmission system includes an error correction encoder part carrying out an error correction encoding for additional data inputted through a first path, a multiplexer (MUX) part, a control part, a channel coding part carrying out an RS encoding and a TCM encoding, and a VSB transmission part modulating the channel-coded data by a VSB method and outputting the modulated data. A receiver system includes a tuner part receiving and tuning additional data and ATSC data transmitted through a same channel, a TCM decoder decoding and outputting the ATSC data and additional data, a deinterleaver deinterleaving data outputted from the TCM decoder, a demultiplexer demultiplexing along a first path (ATSC) or a second path (additional data) in accordance with a kind of output data of the deinterleaver, a limiter carrying out a hard decision on data outputted by the first path, an ATSC decoder part including a derandomizer, and an additional error correction decoder part decoding additional-error-encoded data on additional data outputted through the second path.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/956,070 filed Sep. 19, 2001, now U.S. Pat. No. 7,148,932, whichpursuant to 35 U.S.C. § 119(a), claims the benefit of earlier filingdate and right of priority to Korean Application No. 2000-55854, filedSep. 22, 2000, the contents of which are hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital communication system carryingout modulation/demodulation using a VSB (vestigial side band) method.

2. Background of the Related Art

An 8VSB transmission system for terrestrial wave digital broadcasting istaken as a U.S. standard system in 1995 is test-broadcasted from thelatter half of the year 1998. Such a test broadcasting using aterrestrial wave digital broadcasting standard based on the U.S.standard system is being carried out in Korea as well.

In such a digital broadcasting system, a transmitted signal is receivedby a receiver through a terrestrial channel. In order to restore thesignal in the receiver despite the noise caused by the channel, thesignal is variously coded to be transmitted. In response to the variouscoding process, the receiver carries out the corresponding decodingprocess so as to restore the transmitted signal. U.S. patents, of whichapplicant is Zenith co., such as U.S. Pat. Nos. 5,636,251, 5,629,958,5,600,677 and the like are characterized in that each derandomizercarries out de-randomization by receiving a hard input.

Lately, a broadcasting station tries to transfer such a digitalbroadcasting, which transfers mainly audio and video data, to whichvarious additional data are attached. The additional data includesstock-market information, weather casting, program guide information,HTML, execution files and the like.

Different from general audio/video data in channel transmission, theadditional data are vulnerable fatally to an influence of the channelnoise. For example, the damaged additional data of which informationitself is defected may inform a viewer with wrong information, while thedamaged general audio/video data just result in light image/voice loss.Specifically, when the additional data include numbers or an executionfile, a minor data error causes a devastating result of failing theentire operation.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a digitalcommunication system that substantially obviates one or more problemsdue to limitations and disadvantages of the related art.

An object of the present invention is to provide a VSB transmissionsystem and a reception system thereof fitting for transmittingadditional data as well as robust to a noise.

Another object of the present invention is to provide a VSB transmissionsystem and a reception system thereof compatible with a conventional VSBsystem.

A further object of the present invention is to provide a VSBtransmission system and a reception system thereof enabling to improve adecoding capability for an error correction by receiving a soft input onan additional error correction/restoration.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, atransmission system in a digital TV according to the present inventionincludes an error correction encoder part carrying out an errorcorrection encoding for additional data inputted through a first path, amultiplexer(MUX) part multiplexing ATSC data inputted through a secondpath and the additional data error-correction-encoded through the firstpath so as to output serial data, a control part controlling whether arandomizing is carried out in a path inputted through the first andsecond paths, a channel coding part carrying out an RS encoding and aTCM encoding on a processing result of the randomizing, and a VSBtransmission part modulating the channel-coded data by a VSB method andoutputting the modulated data.

Preferably, the control part bypasses the randomizing when input dataare the additional data inputted through the first path, therebyenabling an additional error correction decoder of a receiver to receivea soft input to be processed. In this case, the ATSC data are audio andvideo data to be transmitted by a conventional VSB method.

In another aspect of the present invention, a receiver system in adigital TV includes a tuner part receiving and tuning additional dataand ATSC data transmitted through a same channel, a TCM decoder decodingand outputting the ATSC data and additional data, a deinterleaverdeinterleaving data outputted from the TCM decoder, a demultiplexerdemultiplexing along a first path (ATSC) or a second path (additionaldata) in accordance with a kind of output data of the deinterleaver, alimiter carrying out a hard decision on data outputted by the firstpath, an ATSC decoder part including a derandomizer, and an additionalerror correction decoder part decoding additional-error-encoded data onadditional data outputted through the second path.

In a further aspect of the present invention, a receiver system in adigital TV includes a tuner part receiving and tuning additional dataand ATSC data transmitted through a same channel, a TCM decoder decodingand outputting the ATSC data and additional data, a deinterleaverdeinterleaving data outputted from the TCM decoder, a demultiplexerdemultiplexing along a first path (ATSC) or a second path (additionaldata) in accordance with a kind of output data of the deinterleaver, alimiter carrying out a hard decision on data outputted by the firstpath, an ATSC decoder part including a derandomizer, and an additionalerror correction decoder part decoding additional-error-encoded data onadditional data outputted through the second path.

Preferably, the TCM decoder in the receiver is a decoder producing asoft output signal with a soft input signal.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a constructional diagram of a transmitter partaccording to the present invention; and

FIG. 2 illustrates a constructional diagram of a receiver part accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Generally, a receiver includes a derandomizer carrying out a hard outputby receiving a hard input, wherein the hard input/output mean that ahard-decision value is inputted and the hard-decision value isoutputted, respectively. On the other hand, soft input/output mean thata value of a probability for a determined value is outputted. Thepresent invention uses an additional error correction encoder, wherebyan additional error correction decoder is necessary. Yet, such anadditional error correction decoder has a poor decoding performance whenan input is a hard input. In order to maximize the decoding performance,the additional error correction decoder should receive a soft input.

Therefore, the additional data processed in the transmitter fail to passthrough a randomizer so as to bypass the randomizer, whereby an input ofthe additional error correction decoder in the receiver enables to havethe soft input.

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 illustrates a basic diagram of a transmitter according to thepresent invention, and FIG. 2 illustrates a constructional diagram of areceiver corresponding to the transmitter in FIG. 1.

Referring to FIG. 1, additional data are encoded by an error correctionencoder via first path. A kind of the encoder depends on a designer'schoice. Thus, the encoder may be one of a convolutional encoder, an RSencoder, a combination of the convolutional/RS encoders and the like.And, general audio/video data as a program are inputted thereto via asecond path, which are the audio/video data compressed by a general MPEGmethod(hereinafter abbreviated ATSC data). The data inputted through thefirst and second paths are multiplexed by a MUX so as to be outputted asa series of serial data. The additional data inputted via the first pathare bypassed without passing through a randomizer, which is controlledby controlling the randomizer in response to a MUXing control signalwhen the MUXing is carried out (not shown in the drawing). The bypassedadditional data experience a channel coding process in a manner ofpassing through an RS encoder adding a parity thereto, an interleavercarrying out an interleaving, and a TCM encoder for a TCM encodingprocess so as to be modulated by a VSB method. Thus, the bypassedadditional data are transmitted in such a way.

Moreover, ATSC data, which are inputted, pass through a channel codingprocess by a conventional terrestrial wave digital method and then aremodulated by a VSB modulation method so as to be transmitted. Namely theATSC data experience a randomizing process and then are outputted to theRS encoder. And, the data, which are transmitted by the VSB modulationmethod finally, include the ATSC and addition data in one channel so asto be transmitted. Of course, the ATSC data can be transmitted onlywithout the additional data.

FIG. 2 illustrates a constructional diagram of a receiver part accordingto the present invention, in which a channel demodulation process iscarried out in response to FIG. 1.

Referring to FIG. 2, a tuner carries out a channel tuning process on thetransmitted data inputted through a terrestrial channel. Then, the tuneddata undergo the processes of a timing recovery, a carrier waverecovery, a channel equalization, a phase correction and the like.Finally, the tuner outputs a baseband signal finally. Such achannel-demodulated signal becomes decoded through a TCM decoder, ofwhich output value is a soft value which is not the value determinedafter the decoding but corresponds to a probability value of its own.This, as mentioned in the above explanation, is for receiving a softinput when the additional error correction decoding is carried out. TheTCM-decoded soft value is deinterleaved by a deinterleaver. A soft valueoutputted by the deinterleaver is then divided into two paths of ATSCand additional data by a deMUX (not shown in the drawing) so as to beoutputted.

In case of ATSC data, a value, which is determined by a decision part(ora limiter) for the soft value outputted by the deinterleaver, isoutputted as a hard value. This is because input and output of the RSdecoder as well as a derandomizer should be the hard values.

The data decoded by the RS decoder are then derandomized by aderandomizer. The derandomized data are outputted to a transport decoderthereafter.

In case of additional data, a decoding process for an additional errorcorrection is carried out on the soft value outputted by the deMUX,before which a parity removal part removing a value corresponding to theRS parity added on transmission is further included. A differencebetween the parity removal part and the above-explained RS decoder liesin whether the decoding process is carried out using the parity value.Namely, the case of ATSC data carries out the RS decoding process usingthe parity. But, the case of additional data removes the parity only.

An error correction process is carried out on the additional dataremoved by the parity removal part by an additional error correctiondecoder which may be designed to correspond to the encoder of thetransmitter. Data outputted from the error correction are finallyoutputted to a transport decoder. Instead, the data outputted from theerror correction decoder may be displayed to a viewer after beingprocessed by an additional processor without passing through thetransport.

The ATSC data are separated into video and audio video data, decoded byan MPEG decoder and an audio decoder respectively, and finally outputtedto a display/speaker.

A TCM decoding algorithm for outputting a soft value according to thepresent invention follows.

As mentioned in the above explanation, in order to maximize aperformance of the additional error correction decoder, a soft outputhas to be produced by a decoder if an internal code. SOVA (soft outputviterbi algorithm) and MAP (maximum A posteriori) are algorithms forproducing a soft output for a trellis coded input column. In aspect of asymbolic error, the MAP algorithm is superior to SOVA. However, theoptimal MAP algorithm has disadvantages such as a calculation ofprobability in an exponential domain and a presumption of a noisevariance of a transmission channel.

Besides, there is SSA (suboptimum soft output algorithm) as a sort ofthe MAP algorithm, in which a probability is calculated in a logarithmicdomain without reducing a performance of the receiver and thepresumption of the noise variance is unnecessary.

Therefore, if the SSA algorithm is used as a decoding algorithm, foursoft outputs, which are shown in the following calculation formula 1,are produced for the input bits d1 and d0 of the encoder.L(00)∝_Log P(d1d0=00|observation)L(01)∝_Log P(d1d0=01|observation)L(10)∝_Log P(d1d0=10|observation)L(11)∝_Log P(d1d0=11|observation) . . . (e1)  [calculation formula 1]

The soft outputs produced by the SSA decoder are measurements of theprobability values for four kinds of combinations of “d1” and “d0”attained after the decoding. Meanwhile, when a convolutional code as anexternal code is used, these soft outputs are directly used as thebranch metric.

As mentioned in the above description, the digital communication systemaccording to the present invention enables to improve a performance bythe additional error correction code of the receiver, thereby increasingaccuracy for additional data.

Moreover, the present invention is compatible with a conventionalreceiver receiving ATSC data.

The forgoing embodiments are merely exemplary and are not to beconstrued as limiting the present invention. The present teachings canbe readily applied to other types of apparatuses. The description of thepresent invention is intended to be illustrative, and not to limit thescope of the claims. Many alternatives, modifications, and variationswill be apparent to those skilled in the art.

1. A method of processing digital broadcast data in a digital broadcastreceiver, the method comprising: receiving the digital broadcast datavia a terrestrial channel, wherein the received digital broadcast datacomprises conventional data multiplexed with additional data, whereinthe conventional data is generated by performing Reed-Solomon (RS)encoding on original conventional data and interleaving the RS encodedoriginal conventional data, wherein the additional data is generated byperforming convolutional encoding on original additional data prior tomultiplexing with the original conventional data, performing RS encodingon the convolutional encoded original additional data and interleavingthe RS encoded original additional data; equalizing the received digitalbroadcast data; decoding the equalized digital broadcast data;separating the decoded digital broadcast data into the conventional dataand the additional data; and removing a Reed-Solomon (RS) parity bitfrom the separated additional data.
 2. A method of processing digitalbroadcast data in a digital broadcast receiver, the method comprising:receiving the digital broadcast data via a terrestrial channel, whereinthe received digital broadcast data comprises conventional datamultiplexed with additional data, wherein the conventional data isgenerated by performing Reed-Solomon (RS) encoding on originalconventional data and interleaving the RS encoded original conventionaldata, wherein the additional data is generated by performingconvolutional encoding on original additional data prior to multiplexingwith the original conventional data, performing RS encoding on theconvolutional encoded original additional data and interleaving the RSencoded original additional data; equalizing the received digitalbroadcast data; decoding the equalized digital broadcast data;separating the decoded digital broadcast data into the conventional dataand the additional data; and performing additional error correctiondecoding on the separated additional data.
 3. A method of processingdigital broadcast data in a digital broadcast receiver, the methodcomprising: receiving the digital broadcast data via a terrestrialchannel, wherein the digital broadcast data comprises conventional datamultiplexed with additional data, wherein the conventional data isgenerated by performing Reed-Solomon (RS) encoding on originalconventional data and interleaving the RS encoded original conventionaldata, wherein the additional data is generated by performingconvolutional encoding on original additional data prior to multiplexingwith the original conventional data, performing RS encoding on theconvolutional encoded original additional data and interleaving the RSencoded original additional data; equalizing the received digitalbroadcast data; decoding the equalized digital broadcast data;separating the decoded digital broadcast data into the conventional dataand the additional data; and removing a Reed-Solomon (RS) parity bitadded in a transmitter from the separated additional data.
 4. A methodof processing digital broadcast data in a digital broadcast receiver,the method comprising: receiving the digital broadcast data via aterrestrial channel, wherein the digital broadcast data comprisesconventional data multiplexed with additional data, wherein theconventional data is generated by performing Reed-Solomon (RS) encodingon original conventional data and interleaving the RS encoded originalconventional data, wherein the additional data is generated byperforming convolutional encoding on original additional data prior tomultiplexing with the original conventional data, performing RS encodingon the convolutional encoded original additional data and interleavingthe RS encoded original additional data; equalizing the received digitalbroadcast data; decoding the equalized digital broadcast data;separating the decoded digital broadcast data into the conventional dataand the additional data; and performing additional error correctiondecoding on the separated additional data.